The present invention is concerned with the field of anchoring of refractory linings to the metallic walls of vessels, conduits and the like.
In many industries such as refineries and chemical processing plants, tanks, conduits and the like are exposed to gases and liquids which are at extremely elevated temperatures and which carry highly erosive particles. These conduits and vessels are lined with refractory material commonly known as refractory concrete which provides both temperature and erosion protection.
One of the major problems encountered in securing the refractory concrete to the vessels and conduits is to provide an anchoring system which will provide the necessary pull strength to prevent the refractory lining from separating from the wall of the vessel or conduit being lined. Additionally, it is a desirable feature of such an anchoring system that the anchoring system itself prevent protection against channeling or erosion of the refractory lining by means of the fluids passing through or upon the surface of the refractory.
One form of refractory anchoring system that has been in use over the years is the hexagonal steel grid. This is a sort of honeycombed appearing steel grid which is welded by hand or otherwise secured to the walls of the vessels or conduits to be lined. The problems with this form of anchor lining system has resulted in entire sections pulling loose which are known as sheet failure or specific areas buckling or pulling away from beneath in what is known as blister failure.
Dr. Michael S. Crowley, working in conjunction with Standard Oil Company of Indiana, designed and developed a refractory anchor system formed of separate and discrete anchors which are hand welded to the wall of the vessel or conduit to be lined with the refractory. These anchors are formed of an S configuration in the upper region thereof and extend down to a weld end. A plurality of these anchors are secured along the metallic wall of the vessel to be lined in random configurations. The extending arms of the S configured anchor provide anchorage for the concrete lining underneath the arms. In a like manner, the S configuration of the arms likewise provide anchoring of the material and also provide deflection and erosion resistance to the refractory material secured by the anchors.
The S configured refractory anchor is the subject matter of U.S. patent application Ser. No. 140,174, filed Apr. 14, 1980. This United States patent application was filed as a European patent application No. 81301620.1 on Apr. 13, 1981. This European patent application has been published as European patent application Publication No. 0038204 on Oct. 21, 1981.
The foregoing European patent application and its counterpart U.S. patent application set forth in detail the background associated with these S configured anchors, the problems experienced in the field, the advantages of the S configured anchor and its solution of these problems and further describe in detail the structure of the S configured anchors.
The subject matter of the present patent application consists of improvements to the Crowley S configured anchor. For this reason, the applicant hereby makes reference to the foregoing Crowley U.S. and European patent applications and incorporates the disclosure thereof into this application by reference thereto. For the convenience of the examiner, a copy of the Crowley European patent application is being filed herewith as Appendix A to this patent application.
The Crowley type S configured anchor is generally formed of 16 gauge material. The weld end is approximately 2 inches in length. The anchors are conventionally welded by hand stick welding on either one or both sides of the weld end of the anchor.
Where the anchors are welded both sides of the anchor, the normal hourly production or welding rate is 12 anchors per hour or approximately 96 anchors per shift. The anchors thus welded demonstrate an approximate pull strength of 7,000 lbs per anchor.
One of the major disadvantages of the Crowley design of refractory anchor is the excessive time that it takes to weld or secure each anchor to the surface to be protected.
The material utilized in the Crowley anchor is 16 gauge stainless steel either 304, 310 or 3/16. This thickness of material, which is approximately 1/16 of an inch and presenting a weld end of approximately 2 inches long, presents a length to width welding surface of approximately 32 to 1.
There has been a desire to utilize the quick and time efficient and inexpensive stud end welding technique for securing the Crowley type anchors. However, for materials of this nature generally, a length to width ratio in excess of 6 to 1 is not acceptable for the stud end welding technique.
It is not practical to reduce the length of the weld end of the Crowley stud while maintaining the same thickness of material to bring the weld surface into the proper ratio inasmuch as this would then reduce the total weld area to a point far below the necessary pull strength required for the anchor. In a like manner, it would not be practical to increase the thickness of the material utilized to fabricate the Crowley type of anchor due to the prohibited increased costs for the anchors due to the increased material.
Accordingly, the problem to be resolved with the Crowley type of refractory anchors is to continue to utilize a material of approximately 16 gauge while, at the same time, fabricating the anchors in their weld end of a type and nature of configuration suitable for welding by the stud end welding technique and retaining the requisite pull strength following the weld.